Cylindrical heat exchanger

ABSTRACT

A cylindrical heat exchanger composed of a cylindrical inner housing formed with smooth internal and external surfaces and a cylindrical outer housing shell formed at opposite ends thereof with a pair of cylindrical portions and at an intermediate portion thereof with a plurality of axially equally spaced annular portions partly reduced in diameter, wherein the outer housing shell is coupled with the inner housing such that the cylindrical portions and annular portions of the outer housing shell are engaged with the external surface of the inner housing to form a plurality of axially spaced annular flow passages communicated with each other through communication passages formed at each one side of the annular portions, and wherein a flow passage composed of the annular flow passages and communication passages is communicated at its one end with an inlet formed in one end portion of the outer housing shell and at its other end with an outlet formed in the other end portion of the outer housing shell.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a cylindrical heat exchanger suitable for use it a freezing system of an auger type ice making machine.

[0003] 2. Description of the Prior Art

[0004] Disclosed in Japanese Patent Laid-open Publication No. 55-25735 is a cylindrical heat exchanger composed of a cylindrical inner housing having smooth internal and external surfaces, a cylindrical outer housing formed at its internal surface with a spiral groove in a predetermined extent and having an inlet and an outlet respectively located at opposite ends of the spiral groove, wherein the inner housing is coupled within the outer housing and is brazed to the internal surface of the outer housing at its smooth external surface in such a manner that the spiral groove is closed by the external surface of the inner housing to form a spiral flow passage of refrigerant.

[0005] As in the cylindrical heat exchanger, the flow passage of refrigerant is in the form of a spiral passage, the refrigerant flows mainly along the internal surface of the outer housing due to a centrifugal force acting thereon in the spiral groove. As a result, the heat exchange of the refrigerant with the outer housing is sufficiently effected, but the heat exchange of the refrigerant with the inner housing is deteriorated. For this reason, ie heat exchange efficiency of the refrigerant with a substance such as fresh water in the inner housing is deteriorated.

SUMMARY OF THE INVENTION

[0006] It is, therefore, a primary object of the present invention to provide a cylindrical heat exchanger capable of enhancing the heat exchange efficiency of the refrigerant with a substance such as fresh water in the inner housing in a simple construction.

[0007] According to the present invention, the object is accomplished by providing a cylindrical heat exchanger composed of a cylindrical inner housing formed with smooth internal and external surfaces and a cylindrical outer housing shell formed at opposite ends thereof with a pair of cylindrical portions and at an intermediate portion thereof with a plurality of axially equally spaced annular portions partly reduced in diameter, wherein the outer housing shell is coupled with the inner housing such that the cylindrical portions and annular portions of the outer housing shell are tightly engaged with the external surface of the inner housing to form a plurality of axially spaced annular flow passages communicated with each other through communication passages formed at each one side of the annular portions, and wherein a flow passage composed of the annular flow passages and communication passages is communicated at its one end with an inlet formed in one end portion of the outer housing shell and at its other end with an outlet formed in the other end portion of the outer housing shell.

[0008] In a practical embodiment of the present invention, the annular flow passages are communicated with each other alternately in a diametrically opposed position through the communication passages, and the cylindrical portions and annular portions of the outer housing shell are brazed to the external surface of the inner housing in a furnace in a condition fixedly coupled therewith.

[0009] In the cylindrical heat exchanger, refrigerant introduced into the inlet of the outer housing shell flows in zigzag alternately through the annular flow passage and communication passage in sequence and discharges from the outlet of the outer housing shell. Thus, the refrigerant flows along each bottom of the annular flow passages at the external surface of the inner housing without causing any flow of refrigerant along the internal surface of the outer housing shell. This is effective to enhance the heat exchange efficiency of refrigerant to ice making water supplied into the inner housing.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Other objects, features and advantages of the present invention will be more readily appreciated from the following detailed description of a preferred embodiment thereof when taken together with the accompanying drawings, in which:

[0011]FIG. 1 is a partly broken sectional view of a cylindrical heat exchanger used in a freezing system of an auger type ice making machine; and

[0012]FIG. 2 is a partly broken sectional view of the cylindrical heat exchanger.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0013] Illustrated in FIG. 1 is a cylindrical heat exchanger 10 in accordance with the present invention, which is used in a freezing system of an auger type ice making machine. The heat exchanger 10 is composed of a cylindrical inner housing 11 formed with smooth internal and external surfaces 11 a and 11 b and a cylindrical outer housing shell 12 formed at its opposite ends with a pair of cylindrical portions 12 a, 12 b of small diameter and at its intermediate portion with a plurality of axially equally spaced annular portions 12 c reduced in diameter. The other components parts such as an auger 21, an extruding head 22, bearing sleeve 23, a lower housing 24, a mechanical seal 25, a connecting sleeve 26, a geared-motor 27 and an ice discharge duct 28 of the ice making machine are conventional component parts well known in this technical field.

[0014] The cylindrical inner housing 11 is made of a metal material such as stainless steel superior in heat transfer and anti-corrosion and is prodded with annular flanges 13, 14 brazed to its stepped portions 11 c, 11 d in a furnace in a condition fixedly coupled therewith. In a brazing process of the annular flanges 13, 14, the stepped portions 11 c, 11 d of inner housing 11 are preliminarily coated with a brazing material. The inner housing 11 has a mounting hole 11 e formed at its lower part 11 e for connection to an inlet pipe 15 of fresh water for ice making, The inlet pipe 15 is brazed in the furnace in a condition fixedly coupled within the mounting hole 11 e, In the brazing process of inlet pipe 15, the external surface 11 a of inner housing 11 is coated with a brazing material at the mounting hole 11 e. The inlet pipe 15 is connected to a water supply pipe for introducing the fresh water for ice making into the interior of inner housing 11 from a water tank (not shown) and to a drain pipe (not shown) for discharging the water from the interior of inner housing 11 into a drain passage (not shown).

[0015] The cylindrical outer housing shell 12 is made of a metallic pipe and is formed in a cylindrical bellows. The outer housing shell 12 has an inlet hole 12 d formed at its upper end portion for connection to an inlet pipe 16 of refrigerant and an outlet hole 12 e formed at its lower end portion for connection to an outlet pipe 17 of the refrigerant. The inlet pipe 16 is brazed in the furnace in a condition fixedly coupled within the inlet hole 12 d of outer housing shell 12 and connected to an expansion valve (not shown) in a freezing system through a freezing circuit (not shown). Similarly, the outlet pipe 17 is brazed in the furnace in a condition fixedly coupled within the outlet hole 12 e of outer housing shell 12 and connected to a compressor in the freezing system through the freezing circuit. The inlet pipe 16 and outlet pipe 17 may be soldered or welded to the outer housing shell 12, respectively. The outer housing shell 12 is formed at its upper end with an annular flange 12 f for engagement with the bottom surface of the annular flange 13 and is formed at its upper and lower ends with radially outwardly turned portions 12 g, 12 h.

[0016] In this embodiment, the outer housing shell 12 is reduced in diameter at its opposite ends to form a pair of cylindrical portions 12 a, 12 b of small diameter and is partly reduced in diameter at its intermediate portion to form a plurality of axially equally spaced annular portions 12 c. During a manufacturing process of the heat exchanger, the inner housing 11 is coupled within the outer housing shell 12 in such a manner that the cylindrical and annular portions 12 a, 12 b and 12 c of outer housing shell 12 are tightly engaged with the surface of inner housing 11 and that the annular flange 12 f of outer housing shell 12 is tightly engaged with the bottom surface of annular flange 13 coupled with the upper end of inner housing 11. In addition, the inlet pipe 15 of fresh water is fixedly coupled with the mounting hole 11 e of inner housing 11. In such a condition described above, the outer housing shell 12 is brazed to the inner housing 11 in the furnace so that a flow passage P of refrigerant is formed between the inner housing 11 and outer housing shell 12.

[0017] The flow passage P of refrigerant is composed of annular flow passages P1 formed at plural steps in an axial direction of the cylindrical inner housing 11 and communicated with each other through communication passages P2 formed at each one side of the annular portions 12 c. The flow passage P of refrigerant is communicated at its one end with the inlet hole 12 d of outer housing shell 12 and at its other end with the outlet hole 12 e of outer housing shell 12. The communication passages P2 are formed alternately in a diametrically opposed position at each step of the annular flow passages P1 to provide the flow passage P in the form of a zigzag passage.

[0018] In the cylindrical heat exchanger described above, the outer housing shell 12 is brazed to the external surface of inner housing 11 in a liquid-tight manner at the cylindrical portions 12 a, 12 b of small diameter and the plurality of axially equally spaced annular portions 12 c partly reduced in diameter to form the plurality of annular flow passages P1 communicated with each other alternately at a circumferentially displaced position through the communication passages P2. In the flow passage P, the refrigerant introduced into the inlet hole 12 d flows in zigzag alternately through the annular flow passage P1 and communication passage P2 in sequence and discharges from the outlet hole 12 e. Thus, the refrigerant flows along each bottom of the annular flow passages P1 at the external surface 11 b of inner housing 11 without causing any flow of refrigerant along the internal surface of outer housing 12 The flow of refrigerant in the flow passage P has been confirmed by an experiment. This is effective to enhance the heat exchange efficiency of refrigerant to the water for ice making supplied into the inner housing 11.

[0019] As in the cylindrical heat exchanger, the communication passages P2 are formed alternately in the diametrically opposed position at each step of the annular flow passages P1, the entire length of the flow passage P from the inlet hole 12 d to the outlet hole 12 e can be prolonged to retain the refrigerant in the flow passage P for an adequate time for enhancing the heat exchange efficiency of refrigerant. As the outer housing shell 12 is integrally assembled with the inner housing 11 by the coupling process and brazing process, the quality of the product is ensured in a stable manner.

[0020] In the manufacturing process of the cylindrical heat exchanger 10, both the annular flanges 13, 14 and the inlet pipe 15 can be brazed to the inner housing 11 in the furnace at the same time during the brazing process of the inner housing 11 and outer housing shell 12. This is useful to eliminate the occurrence of strain caused by local heating during the conventional soldering or welding process.

[0021] In the cylindrical heat exchanger 10, the radially outwardly turned portions 12 g, 12 h formed at the upper and lower ends of outer housing shell 12 are useful to retain the brazing material therein during the brazing process thereby to ensure the integral connection of the cylindrical portions 12 a, 12 b of small diameter with the external surface 11 b of inner housing 11.

[0022] Although in the embodiment described above, the inlet hole 12 d and outlet hole 12 e are formed respectively at the upper and lower end portions of the outer housing shell 12, a pair of inlet holes may be formed at the upper end portion of outer housing shell 12, while a pair of outlet holes may be formed at the lower end portion of outer housing shell 12. Alternatively, the inlet hole 12 d may be formed at the lower end portion of outer housing shelf 12, while the outlet hole 12 e may be formed at the upper end portion of outer housing shell 12.

[0023] Although in the embodiment described above, the communication passages P2 are formed at each one side of the annular portions 12 c partly reduced in diameter, the communication passages P2 may be formed at opposite sides of each annular portion 12 c partly reduced in diameter.

[0024] Although in the embodiment described above, the inner housing 11 is coated at its external surface 11 b with the brazing material prior to the brazing process in the furnace, the outer housing shell 12 may be coated at its internal surfaces with the brazing material. As the integral connection of the annular portions 12 c of outer housing shell 12 with the external surface of inner housing 11 is not required as in the integral connection of the cylindrical portions 12 a, 12 b, the annular portions 12 c of outer housing shell 12 may be fixedly coupled with the external surface of inner housing 11 without brazing thereto.

[0025] In actual practices of the present invention, the cylindrical heat exchanger can be used in a soft-cream maker, a cold carbonated beverage maker or the like 

What is claimed is:
 1. A cylindrical heat exchanger comprising a cylindrical inner housing formed with smooth internal and external surfaces and a cylindrical outer housing shell formed at opposite ends thereof with a pair of cylindrical portions and at an intermediate portion thereof with a plurality of axially equally spaced annular portions partly reduced in diameter, wherein said outer housing shell is coupled with said inner housing such that the cylindrical portions and annular portions of said outer housing shell are tightly engaged with the external surface of said inner housing to form a plurality of axially spaced annular flow passages communicated with each other through communication passages formed at each one side of the annular portions, and wherein a flow passage composed of the annular flow passages and communication passages is communicated at is one end with an inlet formed in one end portion of said outer housing shell and at its other end with an outlet formed in the other end portion of said outer housing shell.
 2. A cylindrical heat exchanges as claimed in claim 1 , wherein said annular flow passages are communicated with each other alternately in a diametrically opposed position through said communication passages.
 3. A cylindrical heat exchanger as claimed in claim 1 , wherein the cylindrical portions and annular portions of said outer housing shell are brazed to the external surface of said inner housing in a furnace in a condition fixedly coupled therewith.
 4. A cylindrical heat exchanger as claimed in claim 1 , wherein the annular portions of said outer housing shell are fixedly coupled with the external surface of said inner housing and wherein the cylindrical portions of said outer housing shell are brazed to the external surface of said inner housing in a furnace. 